Lithium-calcium greases



2,9293 80 LITHIUM-CALC UMGREASE Rosemary OHa'lioran, Union, N.J., ass'ignor to Esso Research and Engineering Company, 'a corporation of Delaware No Drawing. Application September 1, 1955 Serial No. 532,104

3 Claims. (Cl. 252-40) This invention relates to improved lubricating grease compositions and particularly to lithium-calcium eases soap of high" molecular weight fatty acids such :as 12-" hydroxy stearic acid or poly-hydroxy stearic acid.

US. Patent 2,641,577 discloses grease compositions containing a lithium soap and-acalcium soap of-high r molecular weight fatty acids, wherein themol ratjoofthe lithium soap to the calcium soap varies within the range of 2:1 to v8:1. Thepreferred fatty acids employed were the high molecular weight substantially saturated fatty acids such as hydrogenated fish oil acids and stearic acid.

US. Patent 2,646,401'discloses a method of prepar- :cooling to handling temperature without agitation. The

use of unsaturated fatty acids in preparing the lithium and calcium soap thickeners has, however, the disadvantage that lithium soaps having an iodine number above about 45 are soluble in boiling water.

In accordance with this invention it has now been found that lubricating grease compositions containing lithium-calcium soap thickcners prepared from unsaturated fatty acids can be made resistant to boiling water by maintaining the iodine number of the lithium soap below about 40 and by keeping substantially all or a major proportion of the unsaturated fatty acid radicals in the calcium soap portion of the thickener. By this method overall soap thickener iodine numbers of up to about 51 can be tolerated in preparing water resistant, fibrous grease compositions suitable for multi-purpose industrial service.

The lubricating grease compositions of the invention have 11101 ratios of the lithium soap to the calcium soap which may vary between about 2:1 to 8:1, the preferred ratio being within the range of about 3:1 to 6:1. As taught in US. Patent 2,641,577, when the amount of the lithium soap is increased beyond the 8:1 mol ratio the advantages obtained by incorporating the calcium soap decrease markedly. When the amount of the lithium soap is decreased below the 3:1 mol ratio, manufacturing difficulties are encountered.

The'usuai natural or synthetic grease-forming fats or rated high molecular weight fatty acid having an iodine mineral oil, synthetic oil, vegetable 2,929,789 Patented Mar. 2;, 1960 2 fattyacids may be used to formulate the lubricating grease compositions of the invention. Saturated high molecular weight fatty acids having from about 12 to 30 carbon atoms per molecule, preferably from about 18 to 22 carbon atoms per molecule, useful for the purposes of this invention include:

Laurie acid Myristic acid Palmitic acid Stearic acid Arachidic acid Behenic acid Hydrogenated fish oil acids Hydrogenated castor oil acids Hydrogenated tallow acids Monoand poly-hydroxy stearic acids, etc.

The substantially saturated fatty acid described above should have an iodine number of less than about 20,

preferably within the range of about 0 to 15.

Unsaturated fatty acids having from about 12 to 30 carbon atoms, preferably about 18 to 22 carbon atoms, per molecule and unsaturated grease-making fatty material. capable ofbeing employed in this invention include:

9,10-dodecylenic acid Oleic acid Ricinoleic acid Linoleic acid Linoleinic acid Erucic acid Cottonseed fatty acids Fish oil fatty acids Castor oil fatty acids, etc.

Unsaturated fatty acids having an iodine number within the range of about to are preferred, though fatty acids having from about 75 to iodine numbers can also be effectively employed to prepare the greases of the invention.

The lubricating oil base stock serving as a menstruum for the mixture of lithium and calcium soaps may be :1 oil, animal oil, or mixtures thereof. Mineral or synthetic lubricating oils are preferred, and they should have a viscosity within the range of about 50 to 4000 S.U.S. at 100 F. and 30 to 150 S.U.S. at 210 F. Synthetic lubricating oils of the hydrocarbon, hydrocarbon polymer, diester, complex ester, formal, mercaptal, polyalkylene oxide, silicone or similar types can be employed. Synthetic oils such as di-Z-ethylhexyl sebacate, (ii-C Oxo azelate, and other branched chain simple esters of dicarboxylic acids as well as complex esters prepared from glycols, dicarboxylic acids, and alcohols or monocarboxylic acids can also be used. The lithium and calcium soaps are usually employed in proportions of about 5 to 40 weight percent, preferably about 10 to 30 Weight percent, based on the weight of the total composition, to produce the grease compositions of the invention.

In general, the lubricating grease compositions of the invention are prepared under conventional grease-making conditions. A grease base thickened with a lithium soap of saturated, high molecular weight fatty acids having an iodine number of about 0, e.g. stearic acid, and a second grease base thickened with a calcium soap of an.unsatunumber within the range of about 75 to 150, .e. g. oleic acid, are prepared by conventional methods of grease manufacture; The two greases are then blendedtogether by thorough mixing or by the useof a suitable homogenizer or grease mill.

The lithium and calcium soaps may be made either from individual saturated and unsaturated fatty acids, respectively, or from mixtures of saturated and unsaturated fatty acids provided the iodine number of the acids in the lithium soap or soaps is less than 40 and the overall iodine These grease bases were prepared substantially in the same manner as follows. The fatty acid and a quarter of the mineral lubricating oil were heated to about 150 F. The metallic hydroxide in the form of a water slurry number of the mixture of acids in the lithium and calcium (boiling water solution in the case of lithium hydroxide) soaps is not more than about 51, preferably about 30 to was then added to the mixture of fatty acids and mineral 50. oil. The temperature of the resulting mixture was then As noted above, any of the conventional methods of raised to about 200 F. Another quarter of the mineral manufacturing greases may be employed in preparing the lubricating oil charge was then added and the resulting lithium soap thickened grease and the calcium soap l0 grease batch held at 200 F. to 240 F. until dehydration thickened grease. The various constituents are, for was completed. After dehydration the remainder of the example, added to a fire heated kettle and heated to a lubricating oil was added at a temperature of about 300 temperature of from about 220 F. to 250 F. with F. The temperature was held at this point until the grease stirring until dehydration is completed. The tembatch was a homogeneous fluid. The grease batch was perature is then increased to about 300 F. to then cooled to room temperature to obtain the grease 350 F. to melt the soap and to obtain a homogenecompositions set forth in the above table. ous fluid. The resulting grease batch is cooled by draw- Greases E through I, having a mol ratio of lithium ing into thin pans or deep cakes. The grease may also soap to calcium soap of 4 to l (2 to l by weight) were be manufactured in a conventional steam heated kettle at prepared by blending various combinations of the above a temperature of about 325 F., followed by cooling with greases after dehydrating at a temperature of about 250 stirring while running cold water through the kettle F., heating the blend to the melting point of the soap jacket. (about 350 F.), and then pan cooling.

The blending of the lithium soap and the calcium soap The composition and inspection of the final grease thickened greases can be carried out at temperatures of compositions are set forth in Table II below:

Table II Grease No E F G H I J Formulation (Wt. Percent):

Lithium oleate 2.8 4.0-- 6.0..

Lithium stearate..- 5.2-"-.. 4.0-- 2.0-. 8.0--.-" Calcium oieate 4.0 Calcium stearate 4.0 4.0" Mineral lubricating oil (55 88 88 88 88 s.U.s./210 F.). Iodine No. of Fatty Acids:

Lithium soap 32 4' 67.5.. n 25.6..." 32 Calcium soap 0 n 0 on an 90 Totalsoap 21 in 4% an 39.3"... 51. Resistance to boiling water Clean. Slightly Moderately Clean... Clean--- Very Slightly 212 F.) Cloudy. Cloudy. Cloudy.

1 Resistance to boiling water (212 F.) is determined by adding 2 grams of the grease to be tested to a beaker containing cc. of distilled water, boiling for 2 minutes, letting the heated water plus grease stand overnight, and then inspecting the water to see if any solubility of the lithium soap has occurred as evidenced by cloudiness.

about 100 F. to 300 P., preferably about 180 F. to 225 F. The maximum blending temperature employed should be below the temperature at which the lithium grease will undergo a phase change, is. when the grease changes in structure from a rubbery fibrous product to a smooth homogeneous product. As described above, the two grease components are blended together by thorough mixing or by being passed through a Gaulin homogenizer or Morehouse mill.

Although the preparation of separate lithium soap and calcium soap thickened greases followed by blending is the preferred method of preparing the grease compositions of this invention, it is also possible to preform the lithium and calcium soaps with subsequent incorporation directly into the lubricating oil menstruum.

The invention will be more fully understood by reference to the following example illustrating various modiiications of the invention.

EXAMPLE Table I Grease No A B C D Formulation (Wt. Percent):

Lithium 0 m 16 Lithium stear 16 Calcium cleats 8 Calcium stmrnta ,8 Mineral lubricating oil S.U.S.l2l0 F.). 84 92 84 92 The data in Table II show that resistance to boiling water can be imparted to lithium-calcium grease, wherein the soap thickeners are prepared from mixtures of saturated and unsaturated acids, by keeping substantially all or a major proportion of unsaturated acid radicals in the calcium soap. By this method an overall iodine number of up to about 51 can be tolerated, and consequently the large amounts of unsaturated fatty acids required to impart the desirable fibrous structure to the grease can be employed. See greases H and I for the preferred grease compositions of the invention. Greases -F through G, on the other hand, illustrate that where the iodine number of the lithium soap is above about 40 poor resistance to boiling water is found even where the total iodine number of the grease thickeners is less than about 40.

The invention is not necessarily limited to the specific conditions and materials of the foregoing examples. These conditions and materials may be varied within the limits indicated in the general portions of the specification. Moreover, conventional grease additives such as oxidation inhibitors, pour point depressors, corrosion inhibitors, viscosity index improvers and the like can be eifectively incorporated in the grease compositions of this invention.

What is claimed is:

1. A fibrous lubricating grease composition which is resistant to boiling water, comprising a major proportion of lubricating oil thickened to a grease consistency with 5 to 40 weight percent of a mixture of lithium and calcium soaps, said lithium soap being a soap of a C to C fatty acid. having an average iodine number less than 40, said calcium soap being a soap ofa C to C fatty acid having an iodine number of 75 to 150,. the molar ratio of said lithium soap to said calcium soap being about 2:1 to 8:1 and the average iodine number of the total of said fatty acids in said grease composition being about 30 to 50.

2. A method of making a fibrous grease having improved resistance to boiling water which comprises forming a lithium soap of a fatty acid having a chain length in the range of 12 to 30 carbon atoms and an average iodine number less than 40, separately forming a calcium soap of a fatty acid having a chain length in the range of 1'2 to 30 carbon atoms and an iodine number in the range of 75 to 150, and then blending said lithium and calcium soaps in a lubricating oil menstruum at a temperature below that at which the lithium grease undergoes a phase change, the ratio of lithium soap to calcium soap in said menstruum being in the range of 2:1 and 8:1, the amount of said soaps being in the range of 5 to 40 wt. percent based on the final grease composition, and the iodine number of said final grease composition being in the range of to 50.

3. The method of claim 2 wherein said lithium and calcium soaps are separately formed in a lubricating oil menstruum to form greases, and then said greases are blended at a temperature in the range of F. to 300 F., but below that temperature at which the lithium grease undergoes a phase change.

OTHER REFERENCES The Oil and Gas Journal, November 1, 1947, pp. 63 and 69. 

2. A METHOD OF MAKING A FIBROUS GREASE HAVING IMPROVED RESISTANCE TO BOILING WATER WHICH COMPRISES FORMING A LITHIUUM SOAP OF A FATTY ACID HAVING A CHAIN LENGTH IN THE RANGE OF 12 TO 30 CARBON ATOMS AND AN AVERAGE IODINE NUMBER LESS THAN 40, SEPARATELY FORMING A CALCIUM SOAP OF A FATTY ACID HAVING A CHAIN LENGTH IN THE RANGE OF 12 TO 30 CARBON ATOMS, AND AN IODINE NUMBER IN THE RANGE OF 75 TO 150, AND THEN BLENDING SAID LITHIUM AND CALCIUM SOAPS IN A LUBRICATING OIL MENSTRUUM AT A TEMPERATURE BELOW THAT AT WHICH THE LITHIUM GREASE UNDERGOES A PHASE CHANGE, THE RATIO OF LITHIUM SOAP TO CALCIUM SOAP IN SAID MENSTRUUM BEING IN THE RANGE OF 2:1 AND 8:1, THE AMOUNT OF SAID SOAPS BEING IN THE RANGE OF 5 TO 40 WT. PERCENT BASED ON THE FINAL GREASE COMPOSITION, AND THE IODINE NUMBER OF SAID FINAL GREASE COMPOSITION BEING IN THE RANGE OF 30 TO
 50. 